A thin metal plate is being bombarded by a perpendicular beal of gas particles from both sides as shown in the figure. The solid dots are representing the melecules hitting from left side and the faint dots are the molecules hitting frm right side. The mass of these gas particles is `m=10^(-26)kg` and velocity before hitting is `v_(0)=5m//s`. Volume density of the gas particles on both sides is `n=10^(25)` per `m^(3)`. Each beam has an area `A=1m^(2)` and the collisions are perfectly elatic. What is the external force `F` (in newton) required to move the plate with a constant velocity `v=2m//s`

Explanation

`F=2m eta A[(v_(0)+v)^(2)-(v_(0)-v)^(2)]`
`=2(10^(-26))(10^(25))(1)[(5+2)^(2)-(5-2)^(2)]`
`=0.2xx40=8N`